JP2009295300A - Imbalance determination circuit, power supply device, and imbalance determination method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an imbalance determination circuit capable of improving accuracy of determining whether imbalance of an electricity storage exists among each of a plurality of electric storage devices, a method of imbalance determination, and a power supply device using the same. <P>SOLUTION: The invention is equipped with a voltage detection portion 320 to detect each terminal voltage of the electric storage devices B1 to BN connected in series, a gradient grabbing portion 331 which arranges a charge-shutdown while charging, and gets voltage gradient information to show a variation value of each terminal voltage per prescribed period of time under shutdown of the charging concerned, and the imbalance determination portion to find if imbalance of electricity storage is occurring in the electric storage devices B1 to BN by using a plurality of voltage gradient information received by the gradient grabbing portion 331 per each of the terminal voltages. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an imbalance determination circuit, a power supply apparatus, and an imbalance determination method for determining whether or not an imbalance of the amount of electricity stored in a plurality of power storage units has occurred.

  In recent years, power storage devices such as secondary batteries have been widely used as power supply systems in combination with solar cells and power generation devices. The power generation device is driven by natural energy such as wind power or hydraulic power or artificial power such as an internal combustion engine. A power supply system that combines such power storage devices is designed to improve energy efficiency by storing surplus power in the power storage device and supplying power from the power storage device when a load device is required.

  An example of such a system is a solar power generation system. The solar power generation system charges the power storage device with surplus power when the amount of power generated by sunlight is larger than the power consumption of the load device. On the contrary, when the power generation amount is smaller than the power consumption of the load device, the load device is driven by outputting from the power storage device in order to compensate for the insufficient power.

  Thus, in the photovoltaic power generation system, surplus power that has not been used in the past can be stored in the power storage device, so that energy efficiency can be improved compared to a power supply system that does not use the power storage device.

  In such a photovoltaic power generation system, if the power storage device is fully charged, surplus power cannot be charged, and loss occurs. Therefore, in order to efficiently charge the power storage device with surplus power, charge control is performed so that the state of charge of the secondary battery (hereinafter referred to as SOC: State Of Charge) does not become 100%. In addition, charging control is performed so that the SOC does not become 0 (zero)% so that the load device can be driven when necessary. Specifically, in the power storage device, charging control is normally performed so that the SOC changes in the range of 20% to 80%.

  A hybrid electric vehicle (HEV) using an engine and a motor also uses such a principle. When the output from the engine is large relative to the power required for traveling, the HEV drives the generator with the surplus engine output and charges the power storage device. In addition, the HEV charges the power storage device by using the motor as a generator during braking or deceleration of the vehicle.

  In addition, load leveling power sources and plug-in hybrid vehicles that make effective use of nighttime power have recently attracted attention. The load leveling power source is a system that stores power in a power storage device at night when the power consumption is low and the power rate is low, and uses the stored power during the day when the power consumption peaks. The purpose is to make the power generation amount constant by smoothing the power consumption, and to contribute to the efficient operation of power facilities and the reduction of capital investment.

Plug-in hybrid vehicles use nighttime power, mainly EV driving that supplies power from the power storage device when driving in urban areas with poor fuel efficiency, and by HEV driving using the engine and motor during long distance driving, The goal is to reduce total CO ₂ emissions.

  By the way, such a power storage device is configured by connecting a plurality of power storage elements (single cells or the like) in series in order to obtain a desired output voltage. In such a power storage element, when a deep discharge is performed in a state where the amount of stored charge of each power storage element varies, the power storage element with a small amount of stored charge is further overdischarged, and the power storage element deteriorates and the entire power storage device This will reduce the lifespan.

In order to suppress such deterioration of the lifetime of the power storage device, a technique is known in which when the amount of stored charge (SOC) varies, the variation in the stored charge amount is eliminated using an equalizing means. As a means for equalization, a method is disclosed in which the lowest voltage and the terminal voltage of each power storage element are compared and equalized when the voltage difference exceeds a predetermined value (see, for example, Patent Document 1).
JP-A-8-19188

  However, in the method disclosed in Patent Document 1 described above, as a means for equalization, the lowest voltage and the terminal voltage of each power storage element are compared, and the equalization determination is made when the voltage difference becomes a predetermined value or more. For this reason, in a storage element having a characteristic in which a change in OCV (Open Circuit Voltage) with respect to a change in SOC is small, the amount of stored charge is not reflected in the voltage difference. Decreases.

  FIG. 10 is a graph showing the relationship between the SOC and the terminal voltage of a secondary battery (for example, a lithium ion secondary battery). In FIG. 10, the horizontal axis indicates the SOC, and the vertical axis indicates the terminal voltage when the secondary battery is not loaded, that is, the OCV. As shown by a graph G101 in FIG. 10, the terminal voltage of the secondary battery generally increases as the charging progresses and the SOC increases.

  Therefore, in the case of the power storage element having the properties shown in the graph G101, the change in the stored charge amount is easily reflected in the terminal voltage, so that the detection accuracy of the stored charge amount variation is good.

  However, some power storage elements have a flat voltage characteristic with a small change in terminal voltage with respect to a change in SOC, that is, the amount of stored charge, as indicated by a graph G102 in FIG. In this way, in the case of a power storage element in which the change in terminal voltage is flat with respect to the change in SOC, the terminal voltage changes gently with respect to the change in SOC. Therefore, if the SOC is detected based on the terminal voltage, The detection accuracy of variation will be reduced. For example, there is a possibility that the actual SOC is 20% but erroneously detected as 80%.

  When the detection accuracy of the stored charge amount variation decreases, the storage device is charged / discharged while the stored charge amount variation occurs, and a plurality of storage elements with a small stored charge amount are overdischarged, As a result of overcharging those having a large amount of charge, there is a disadvantage that the power storage element deteriorates and the life deterioration of the entire power storage device is accelerated.

  The present invention has been made in view of such circumstances, and an imbalance determination circuit that can improve the accuracy of determining whether or not an imbalance has occurred in each storage amount in a plurality of power storage units, An object of the present invention is to provide a balance determination method and a power supply device using the same.

  The imbalance determination circuit according to the present invention includes a voltage detection unit that detects a terminal voltage in each of the plurality of power storage units, and stops the charging while the plurality of power storage units are being charged, and detects the voltage while the charging is stopped. An inclination acquisition unit that performs an inclination information acquisition process for acquiring voltage inclination information indicating a change amount of each terminal voltage per predetermined time from each terminal voltage detected by the unit; And an imbalance determination unit that determines whether or not an equilibrium has occurred using a plurality of pieces of voltage gradient information corresponding to the terminal voltages acquired by the gradient acquisition unit.

  Further, in the imbalance determination method according to the present invention, the voltage detection unit detects each of the terminal voltages in the plurality of power storage units, and the slope acquisition unit stops the charging during the charging of the plurality of power storage units. And a step of performing slope information acquisition processing for acquiring voltage slope information indicating a change amount of each terminal voltage per predetermined time from each terminal voltage detected by the voltage detection unit while the charging is stopped, and imbalance A step of determining, using a plurality of pieces of voltage gradient information corresponding to each terminal voltage acquired by the gradient acquisition unit, whether or not a determination unit has an imbalance in the amount of electricity stored in the plurality of power storage units; including.

  According to this configuration, the inclination acquisition unit stops the charging during charging of the plurality of power storage units, and from each terminal voltage detected by the voltage detection unit during the charging stop, the terminal voltage per predetermined time. Voltage gradient information indicating the amount of change is acquired. Then, using the voltage gradient information acquired by the gradient acquisition unit, the imbalance determination unit determines whether or not there is an imbalance in the amount of power stored in the plurality of power storage units. In this case, even when a power storage unit having a small change in terminal voltage with respect to a change in power storage amount is used, it is determined whether or not there is an imbalance in the power storage amount among a plurality of power storage units based on the voltage slope information. By determining, it is possible to improve the determination accuracy of whether or not each storage amount has an imbalance as compared to the case of determining the presence or absence of an imbalance based on the SOC directly converted from the terminal voltage as in the background art. it can.

  In addition, the imbalance determination unit may determine whether or not there is an imbalance in the amount of power stored in the plurality of power storage units by using different determination processes using the plurality of voltage gradient information acquired by the gradient acquisition unit. Final determination for finally determining whether or not there is an imbalance in the amount of electricity stored in the plurality of power storage units based on the determination results by the plurality of preliminary determination units and the plurality of determination processing units. It is preferable to provide a part.

  According to this configuration, the plurality of preliminary determination units use the plurality of voltage gradient information acquired in correspondence with each terminal voltage by the gradient acquisition unit, and the amount of power storage in the plurality of power storage units is determined by different determination processes. A preliminary determination is made as to whether an equilibrium has occurred. Then, the final determination unit finally determines whether or not there is an imbalance in the amount of power stored in the plurality of power storage units based on a plurality of preliminary determination results from different determination processes. Compared with the case where it is determined whether or not there is an imbalance in the amount of stored electricity based on the determination processing result, it is possible to improve the determination accuracy of whether or not there is an imbalance in the amount of stored electricity.

  In addition, one of the plurality of preliminary determination units has a difference between voltage gradient information acquired by the gradient acquisition unit exceeding a preset first determination value immediately after the charging is stopped. It is preferable to preliminarily determine that the imbalance has occurred.

  According to this configuration, one of the plurality of preliminary determination units determines whether or not an imbalance has occurred based on the difference between the pieces of voltage gradient information acquired by the gradient acquisition unit immediately after stopping charging. Since preliminary determination can be performed, it is easy to shorten the determination time.

  In addition, one of the plurality of preliminary determination units is configured such that a difference between the respective voltage gradient information acquired by the gradient acquisition unit is set in advance when a preset set time has elapsed since the charging is stopped. It is preferable to preliminarily determine that the imbalance has occurred when the determined second determination value is exceeded.

  According to this configuration, when a preset set time has elapsed from the stop of charging, the voltage gradient information obtained from each power storage unit and the power storage amount of each power storage unit have a correlation, so that a plurality of preliminary determination units One of the cases is that if the difference between the respective voltage slope information acquired by the slope acquisition unit exceeds a preset second determination value when a preset set time has elapsed since the stop of charging, It can be preliminarily determined that an equilibrium has occurred.

  In addition, one of the plurality of preliminary determination units is configured such that each of the elapsed time from the stop of charging when each voltage gradient information acquired by the gradient acquisition unit becomes equal to a preset reference value. When the difference between them exceeds a preset third determination value, it is preferable to preliminarily determine that the imbalance has occurred.

  According to this configuration, when each voltage gradient information acquired by the gradient acquisition unit is equal to a preset reference value, there is a correlation between the elapsed time from the stop of charging and the charged amount of each power storage unit Therefore, one of the plurality of preliminary determination units is based on the relationship between the elapsed time from the stop of charging when each voltage gradient information acquired by the gradient acquisition unit is equal to a preset reference value. If the difference exceeds the third determination value set in advance, it can be preliminarily determined that an imbalance has occurred.

  In addition, it is preferable that the final determination unit finally determines that the imbalance has occurred when all of the plurality of preliminary determination units have determined that the imbalance has occurred.

  According to this configuration, when all of the plurality of preliminary determination units determine that an imbalance has occurred, the final determination unit finally determines that an imbalance has occurred. Certainty is improved and frequent equalization processing due to erroneous determination can be prevented.

  The final determination unit may finally determine that the imbalance has occurred when at least one of the plurality of preliminary determination units determines that the imbalance has occurred. .

  According to this configuration, when at least one of the plurality of preliminary determination units determines that an imbalance has occurred, the final determination unit finally determines that an imbalance has occurred. It is possible to reduce the possibility of detection omission.

  Moreover, it is preferable that the said electrical storage body becomes so that the fall amount per predetermined time of the terminal voltage after stopping charging becomes large, so that the electrical storage amount increases.

  According to this configuration, the difference in the amount of electricity stored in each power storage unit is obtained as the difference in the amount of decrease in the terminal voltage of each power storage unit per predetermined time after the charging is stopped. It becomes easy to determine whether or not an equilibrium has occurred.

  Moreover, it is preferable that the said electrical storage body is a lithium ion secondary battery using the olivine type lithium composite phosphate as a positive electrode active material.

  Lithium ion secondary batteries that use olivine-based lithium composite phosphate as the positive electrode active material have a larger amount of decrease in terminal voltage that occurs when charging is stopped. Is preferred.

Also, the positive electrode active _{material, Li X A Y B Z PO} 4 (A is, Me, at least one of Fe, Mn, Co, Ni, Cu, B is, Mg, Ca, Sr, Sc , Y, Ti , Zr, V, Nb, Cr, Mo, W, Ag, Zn, In, Sn, Sb, 0 <X ≦ 1, 0.9 ≦ Y ≦ 1, 0 ≦ Z ≦ 0.1) Preferably there is.

As a positive electrode active _{material, Li X A Y B Z PO} 4 (A is, Me, Fe, Mn, Co , Ni, at least one of Cu, B is, Mg, Ca, Sr, Sc , Y, Ti, Zr, Lithium using at least one of V, Nb, Cr, Mo, W, Ag, Zn, In, Sn, and Sb, 0 <X ≦ 1, 0.9 ≦ Y ≦ 1, 0 ≦ Z ≦ 0.1) An ion secondary battery is suitable as the above-described power storage unit because the amount of decrease in terminal voltage that occurs when charging is stopped increases as the amount of stored power increases.

  Moreover, it is preferable that the said inclination acquisition part performs the said inclination information acquisition process, when each terminal voltage detected by the said voltage detection part exceeds the preset reference voltage.

  When the power storage amount of each power storage unit is small, it is considered that there is little need to reduce the power storage amount imbalance. Therefore, when each terminal voltage detected by the voltage detection unit exceeds a preset reference voltage and it is considered that there is a certain amount of stored electricity, the inclination information acquisition process is performed by performing the inclination information acquisition process. It is possible to reduce the execution frequency. Since charging is stopped in the inclination information acquisition process, if the frequency of execution of the inclination information acquisition process is reduced, the opportunity to stop charging is reduced. The risk of being lost is reduced.

  Moreover, it is preferable that the said voltage detection part is provided with the several voltage measurement part which detects the terminal voltage of each said electrical storage body.

  According to this configuration, since the terminal voltage of each power storage unit can be detected at the same time, it is easy to shorten the detection time of the terminal voltage of each power storage unit.

  In addition, the voltage detection unit switches a connection relationship between the voltage measurement unit that detects a terminal voltage of each power storage unit, and the voltage measurement unit and each power storage unit, and the voltage measurement unit causes each of the power storage units to be switched. You may make it provide the switching part which detects each terminal voltage of a body.

  According to this configuration, the terminal voltage of each power storage unit can be detected by providing only one voltage measuring unit, so that space saving and cost reduction are facilitated.

  Further, the power supply device according to the present invention includes the imbalance determination circuit, the plurality of power storage units, a discharge unit that discharges the plurality of power storage units, and the imbalance determination unit. A forced discharge control unit for discharging each power storage unit by the discharge unit until a terminal voltage detected by the voltage detection unit is equal to or lower than a preset target voltage when it is determined that the voltage detection unit has occurred. Prepare.

  According to this configuration, when an imbalance in the storage amount of each power storage unit is detected by the above-described imbalance determination circuit, the discharge unit discharges each terminal voltage of each power storage unit to a target voltage or less, Imbalance is reduced.

  In the charge control circuit and the charge control method configured as described above, the slope acquisition unit stops the charging during charging of the plurality of power storage units, and each terminal voltage detected by the voltage detection unit while the charging is stopped. Thus, voltage gradient information indicating the amount of change of each terminal voltage per predetermined time is acquired. Then, using the voltage gradient information acquired by the gradient acquisition unit, the imbalance determination unit determines whether or not there is an imbalance in the amount of power stored in the plurality of power storage units. In this case, even when a power storage unit having a small change in terminal voltage with respect to a change in power storage amount is used, it is determined whether or not there is an imbalance in the power storage amount among a plurality of power storage units based on the voltage slope information. By determining, it is possible to improve the determination accuracy of whether or not each storage amount has an imbalance as compared to the case of determining the presence or absence of an imbalance based on the SOC directly converted from the terminal voltage as in the background art. it can.

  Embodiments according to the present invention will be described below with reference to the drawings. In addition, the structure which attached | subjected the same code | symbol in each figure shows that it is the same structure, The description is abbreviate | omitted. FIG. 1 is a block diagram illustrating an example of a configuration of an imbalance determination circuit using an imbalance determination method according to an embodiment of the present invention, a power supply device including the imbalance determination circuit, and a power supply system.

  A power supply system 1 illustrated in FIG. 1 includes a power generation device 10, a power supply control device 30, and a power storage device 40. The power supply control device 30 and the power storage device 40 constitute a power supply device 50. The power supply device 50 includes, for example, a battery pack, an uninterruptible power supply device, a power generation device that utilizes natural energy, a power storage device that stores surplus power of a power generation device that uses an engine as a power source, a load leveling power source, and the like Used as various power supply devices. The power device 50 is connected to the load device 20 that receives power from the power generation device 10 and the power storage device 40.

  Specifically, the power generation device 10 is, for example, a power generation device using natural energy such as a solar power generation device (solar cell) or a generator using an engine as a power source. The power supply device 50 may be configured to receive power supply from a commercial power supply instead of the power generation device 10.

  The power storage device 40 is configured by connecting N power storage units B1, B2,..., BN in series. The power storage units B1, B2,..., BN are accommodated in a box (not shown). In addition, each of the power storage units B1, B2,..., BN is configured by electrically connecting a plurality of power storage elements 401 in series. As each power storage element 401, an alkaline storage battery such as a nickel metal hydride battery, an organic battery such as a lithium ion battery, and a power storage element such as an electric double layer capacitor can be used.

  For example, as shown in a graph G102 in FIG. 10, the power storage element 401 has a flat characteristic in which a change in terminal voltage is small with respect to a change in SOC. As shown in the graphs G1 and G2 in FIG. 2, the storage element 401 has a storage element that increases as the storage amount increases, that is, the closer to full charge, the lower the terminal voltage until the steady value is reached after the charge is stopped. It is used.

Specifically, a lithium ion secondary battery using LiFePO ₄ which is an example of an olivine-based lithium composite phosphate can be suitably used as the power storage element 401, for example, as a positive electrode active material. Incidentally, the positive electrode active material, for _{example, Li X A Y B Z PO} 4 (A is Me, Fe, Mn, Co, Ni, at least one of Cu, B is Mg, Ca, Sr, Sc, Y, At least one of Ti, Zr, V, Nb, Cr, Mo, W, Ag, Zn, In, Sn, and Sb, 0 <X ≦ 1, 0.9 ≦ Y ≦ 1, 0 ≦ Z ≦ 0.1) More preferably, it may be LixFePO ₄ (0 <x ≦ 1).

A lithium ion secondary battery using LiFePO ₄ as a positive electrode active material is flat with a small change in terminal voltage with respect to a change in SOC in a wide region, for example, as shown in a graph G102 in FIG. For example, a secondary battery in which the amount of change in terminal voltage when the SOC changes from 10% to 95% is 0.01 V or more and less than 0.3 V can be used as the power storage element 401.

In addition, as shown in FIG. 2, the inventors of the present application, as shown in FIG. 2, in the lithium ion secondary battery using LiFePO ₄ as the positive electrode active material, the amount of decrease in the terminal voltage per predetermined time after stopping the charge is less than the SOC. It has been found experimentally that it has the property of becoming larger as it becomes larger.

  FIG. 2 is an explanatory diagram for explaining a change in the terminal voltage (OCV) when the charging current is made zero after charging current is passed through the storage element 401 (when charging is stopped). Graph G1 shows a case where charging is stopped when the SOC is 100%, and graph G2 shows a case where charging is stopped when the SOC is 70%. The vertical axis in FIG. 2 indicates the terminal voltage (OCV) of the power storage element 401, and the horizontal axis indicates the elapsed time since charging was stopped.

  At this time, the inventors of the present application indicated that the slope of the terminal voltage drop curve after stopping the charging, that is, the amount of decrease in the terminal voltage per predetermined time after the charging was stopped, as shown in FIG. It was experimentally found that when the SOC of 401 is small (graph G2), the storage element 401 is fully charged (graph G1).

  Note that the number of power storage units, the number of power storage elements 401, and the connection state are not particularly limited. For example, each power storage unit may be configured by connecting a plurality of power storage elements 401 in series, parallel, or a mixture of series and parallel. Each power storage unit may be one power storage element 401. Further, the configuration of the power storage device 40 is not limited to the above.

  The power supply control device 30 is configured as an in-vehicle ECU (Electric Control Unit), for example. The power supply control device 30 includes a discharge unit 310, an imbalance determination circuit 350, and a charge / discharge control circuit 340. The imbalance determination circuit 350 includes a voltage detection unit 320 and a control unit 330.

  The charge / discharge control circuit 340 charges the power storage device 40 with, for example, surplus power generated in the power generation device 10 or regenerative power generated in the load device 20. Further, when the current consumption of the load device 20 suddenly increases or the power generation amount of the power generation device 10 decreases and the power required by the load device 20 exceeds the output of the power generation device 10, the charge / discharge control circuit 340 Thus, the insufficient power is supplied from the power storage device 40 to the load device 20. Further, the charge / discharge control circuit 340 stops or permits charging of the power storage device 40 in accordance with a control signal from the control unit 330.

  Thus, the charge / discharge of the power storage device 40 is controlled by the charge / discharge control circuit 340, so that the SOC of the power storage device 40 is in a range of about 20 to 80% in a normal case. Alternatively, in a load leveling power source or a plug-in hybrid vehicle that effectively uses nighttime power, the power storage device 40 is charged to a state where the SOC is 100%, and the load device 20 is discharged when energy is required. It has become.

  The voltage detector 320 detects the terminal voltages V1, V2,..., VN of the power storage units B1, B2,..., BN, and outputs the detected values to the controller 330. FIG. 3 is a block diagram showing an example of the configuration of the voltage detection unit 320 shown in FIG. The voltage detection unit 320 illustrated in FIG. 3 includes, for example, an analog-digital converter 321 (voltage measurement unit) and a switching circuit 322 (switching unit). Note that the voltage measurement unit is not limited to an analog-digital converter, and may be a voltage detection circuit such as a comparator, for example.

  The switching circuit 322 is configured using, for example, a plurality of switching elements. Then, the switching circuit 322 turns on and off the plurality of switching elements in accordance with a control signal from the control unit 330, thereby causing the terminal voltages V1, V2,... BN of the power storage units B1, B2,. Select one of VN and output to analog-digital converter 321.

  The analog-digital converter 321 converts the voltage output from the switching circuit 322 into a digital value and outputs the digital value to the control unit 330.

  As a result, the control unit 330 sequentially selects the terminal voltages V1, V2,..., VN by the switching circuit 322, so that the terminal voltages V1, V2,. , And data indicating terminal voltages V1, V2,..., VN are acquired.

  Accordingly, since only one voltage measuring unit such as the analog-digital converter 321 need be provided regardless of the number of power storage units, space saving and cost reduction are facilitated.

  For example, as shown in FIG. 4, the voltage detection unit 320a may be configured by N voltage measurement units 323 that respectively detect the terminal voltages V1, V2,..., VN. In this case, since the terminal voltages V1, V2,..., VN can be detected simultaneously, the detection time of the terminal voltages V1, V2,.

  The discharging unit 310 includes N resistors R1, R2,..., RN and N transistors Q1, Q2,. A series circuit of the resistor R1 and the transistor Q1 is connected in parallel to the power storage unit B1, a series circuit of the resistor R2 and the transistor Q2 is connected in parallel to the power storage unit B2, and so on. A circuit is connected in parallel with each power storage unit.

  The transistors Q1, Q2,..., QN are turned on and off in accordance with the equalized discharge signals SG1, SG2,. When the transistors Q1, Q2,..., QN are turned on, the power storage body connected in parallel with the turned-on transistors is discharged through a resistor.

  The control unit 330 includes, for example, a CPU (Central Processing Unit) that executes predetermined arithmetic processing, a ROM (Read Only Memory) that stores a predetermined control program, and a RAM (Random Access Memory) that temporarily stores data. And a timer circuit 337 and peripheral circuits thereof.

  Then, the control unit 330 executes a control program stored in the ROM, for example, to thereby obtain an inclination acquisition unit 331, a first preliminary determination unit 332, a second preliminary determination unit 333, a third preliminary determination unit 334, and a final determination unit. 335 and the forced discharge control unit 336. In this case, the first preliminary determination unit 332, the second preliminary determination unit 333, the third preliminary determination unit 334, and the final determination unit 335 correspond to an example of an imbalance determination unit. Note that the charge / discharge control circuit 340 and the load device 20 may be configured to include a part or all of the control unit 330.

  The inclination acquisition unit 331 stops the charging by the charge / discharge control circuit 340 while the power storage device 40 is being charged, and the power storage units B1, B2,... Detected by the voltage detection unit 320 while the charging is stopped. From the terminal voltage of BN, voltage slope information indicating the amount of decrease per unit time of the terminal voltage is acquired.

  As the first preliminary determination process, the first preliminary determination unit 332 has a difference between the pieces of voltage gradient information acquired by the gradient acquisition unit 331 exceeding a preset first determination value γ1 immediately after stopping charging. Then, it is preliminarily determined that there is an imbalance in the amount of electricity stored in power storage units B1, B2,.

  As the second preliminary determination process, the second preliminary determination unit 333 is configured such that a difference between the respective voltage gradient information acquired by the gradient acquisition unit 331 is obtained when a preset set time β has elapsed from the stop of charging. When the preset second determination value γ2 is exceeded, it is preliminarily determined that there is an imbalance in the storage amount of the power storage units B1, B2,.

  As the third preliminary determination process, the third preliminary determination unit 334 determines the elapsed time from the stop of charging when each voltage gradient information acquired by the gradient acquisition unit 331 becomes equal to the preset reference value ε. When the difference between them exceeds a preset third determination value γ3, it is preliminarily determined that there is an imbalance in the storage amount of the power storage units B1, B2,.

  When the final determination unit 335 preliminarily determines that an imbalance has occurred, all of the first preliminary determination unit 332, the second preliminary determination unit 333, and the third preliminary determination unit 334 as a final determination process. It is finally determined that there is an imbalance in the amount of electricity stored in power storage units B1, B2,.

  When the final determination unit 335 determines that an imbalance has occurred, the forced discharge control unit 336 has preset terminal voltages V1, V2,..., VN detected by the voltage detection unit 320, respectively. By discharging the power storage units B1, B2,..., BN by the discharge unit 310 until the target voltage α2 or less, the variation in the stored charge amount in the power storage units B1, B2,. Reduce equilibrium.

  The timer circuit 337 is used for causing the voltage detection unit 320 to periodically detect, for example, the terminal voltages V1, V2,..., VN every unit time, or to measure the elapsed time from the stop of charging. It is done.

  Next, the operation of the power supply device 50 shown in FIG. 1 will be described. 5 to 9 are flowcharts showing an example of the operation of the power supply device 50 shown in FIG. First, the charging / discharging control circuit 340 supplies a charging current from the power generation device 10 to the power storage device 40, and charging of the power storage device 40 is started (step S1).

  Next, the switching circuit 322 sequentially switches the terminal voltage to be detected in accordance with a control signal from the control unit 330, so that each of the power storage units B1, B2,. Terminal voltages V1, V2,..., VN are detected (step S2). Note that the terminal voltages V1, V2,..., VN may be detected simultaneously by the voltage detector 320a.

  Next, the first preliminary determination unit 332 compares the terminal voltages V1, V2,..., VN with a preset reference voltage α1 (step S3). If any one of the terminal voltages V1, V2,..., VN does not satisfy the reference voltage α1, the process returns to step S2 to detect the terminal voltages V1, V2,. Is repeated (NO in step S3). On the other hand, if all of the terminal voltages V1, V2,..., VN are equal to or higher than the reference voltage α1 (YES in step S3), the process proceeds to step S4 so as to make a preliminary determination of the unbalance of the storage amount.

  Accordingly, the determination of imbalance is made after all of the power storage units B1, B2,..., BN are charged to the reference voltage α1 or higher.

  As will be described later, when the final determination unit 335 determines that an imbalance has occurred, the forced discharge control unit 336 causes the power storage units B1, B2,... Until the terminal voltage becomes equal to or less than the target voltage α2, respectively. , BN, respectively, to reduce the imbalance. Therefore, when the terminal voltage of the power storage units B1, B2,... BN is lower than the target voltage α2 before the discharge by the forced discharge control unit 336, the imbalance cannot be reduced by the discharge. .

  However, by setting the reference voltage α1 to a voltage value equal to or higher than the target voltage α2, the terminal voltages of the power storage units B1, B2,... BN are set to be equal to or higher than the target voltage α2, and the imbalance is reduced by discharging. Has been made possible.

  In step S4, the first preliminary determination unit 332 outputs a control signal requesting to stop charging to the charge / discharge control circuit 340, and the charge / discharge control circuit 340 reduces the charge / discharge current of the power storage device 40 to zero. Charging is stopped (step S4).

  Then, the first preliminary determination unit 332 starts the timer circuit 337 (step S5). Then, the timer circuit 337 measures the elapsed time from the stop of charging.

  Next, the slope acquisition unit 331 causes the voltage measurement unit 323 to measure the terminal voltages V1, V2,..., VN every predetermined time, for example, every unit time. Then, the slope acquisition unit 331 determines, for each unit time, the difference between the previous measurement value of the terminal voltages V1, V2,..., VN and the current measurement value as a voltage change amount dV, which is an example of voltage slope information. / Dt is calculated (step S6). Thereafter, the calculation of the voltage change amount dV / dt is continuously executed while the first, second, and third preliminary determination processes are being executed.

  Note that the voltage change amount dV / dt is not limited to the example measured every unit time, and the slope acquisition unit 331 may convert the voltage change amount per unit time, and the voltage slope remains the change amount per predetermined time. It may be used as information. Hereinafter, the voltage change amounts dV / dt of the terminal voltages V1, V2,..., VN are referred to as voltage change amounts dV (1), dV (2),.

  Next, “1” is assigned to the variable n by the first preliminary determination unit 332 (step S7). Then, the first preliminary determination unit 332 compares the absolute value of dV (n) −dV (n + 1), that is, the difference between the voltage change amounts dV / dt in the adjacent power storage units with the first determination value γ1 (step) S8).

  If the absolute value of dV (n) −dV (n + 1) is larger than the first determination value γ1 (YES in step S8), it is determined that an imbalance that requires correction is generated in the stored charge amount. The first determination flag Flag1 is turned on (step S9), and the process proceeds to the second and third preliminary determination processes. The second and third preliminary determination processes are executed in parallel.

  On the other hand, if the absolute value of dV (n) −dV (n + 1) is equal to or smaller than the first determination value γ1 (NO in step S8), the first preliminary determination unit 332 adds “1” to the variable n ( Step S10). Next, the first preliminary determination unit 332 compares the variable n with the number N of power storage units (step S11).

  If the variable n is less than the number N of power storage units (NO in step S11), the process proceeds to step S8 again to determine the imbalance for the next power storage unit. On the other hand, if variable n is greater than or equal to the number N of power storage units (YES in step S11), the determination of imbalance for all power storage units is completed, and the process proceeds to step S12.

  Next, in step S12, the first preliminary determination unit 332 compares the timer value T of the timer circuit 337 with a preset monitoring time Tlim (step S12). The monitoring time Tlim is set to, for example, the time from when charging is stopped until the terminal voltages V1, V2,..., VN of the power storage units B1, B2,.

  That is, when the time equal to or longer than the monitoring time Tlim elapses after the charging is stopped, the terminal voltages V1, V2,..., VN are in a steady state and do not change. Then, it becomes impossible to determine imbalance based on the amount of change in terminal voltage.

  Therefore, when the timer value T becomes equal to or longer than the monitoring time Tlim (YES in step S12), the process is forcibly terminated without shifting to the second and third preliminary determination processes. On the other hand, if the timer value T does not reach the monitoring time Tlim (NO in step S12), the process proceeds to the second and third preliminary determination processes.

  Next, the second preliminary determination process will be described. FIG. 6 is a flowchart illustrating an example of the second preliminary determination process. In the second preliminary determination process, first, the second preliminary determination unit 333 determines whether or not the first determination flag Flag1 is ON (step S21). If the first determination flag Flag1 is not ON (NO in step S21), the second preliminary determination process is terminated and the process proceeds to the final determination process.

  Note that if the time for which charging is stopped for the equalization process becomes long, the use of the power supply system 1 is hindered. Therefore, the monitoring time Tlim is charged for the equalization process during use of the power supply system 1. You may make it set the time which does not interfere with stopping.

  In the final determination process, when the final determination unit 335 preliminarily determines that all of the first preliminary determination unit 332, the second preliminary determination unit 333, and the third preliminary determination unit 334 are imbalanced, That is, when all of the first determination flag Flag1, the second determination flag Flag2, and the third determination flag Flag3 are on, there is an imbalance in the storage amount of the power storage units B1, B2,. Since the determination is made, if the first determination flag Flag1 is not ON (NO in step S21), it is clear that the final determination unit 335 determines that no imbalance has occurred at this point, so steps S22 to S28. The processing load is reduced by omitting the execution of.

  On the other hand, if the first determination flag Flag1 is ON (YES in step S21), the process proceeds to step S22.

  Next, in step S22, the second preliminary determination unit 333 compares the timer value T of the timer circuit 337 with the set time β (step S22). When the timer value T becomes equal to or longer than the set time β (YES in step S22), the second preliminary determination unit 333 substitutes “1” for the variable n (step S23).

  Then, when the timer value T becomes equal to or greater than the set time β by the second preliminary determination unit 333, that is, when the set time β has elapsed from the stop of charging, the voltage change amount dV / Based on dt, an absolute value of dV (n) −dV (n + 1), that is, a difference in voltage change amount dV / dt between adjacent power storage units is calculated and compared with the second determination value γ2 (step S24).

  If the absolute value of dV (n) −dV (n + 1) is larger than the second determination value γ2 (YES in step S24), it is determined that an imbalance that requires correction is generated in the stored charge amount. Then, the second determination flag Flag2 is turned on (step S25), and the process proceeds to the final determination process.

  On the other hand, if the absolute value of dV (n) −dV (n + 1) is equal to or smaller than the second determination value γ2 (NO in step S24), the second preliminary determination unit 333 adds “1” to the variable n ( Step S26). Next, the second preliminary determination unit 333 compares the variable n with the number N of power storage units (step S27).

  If the variable n is less than the number N of power storage units (NO in step S27), the process proceeds to step S24 again to determine the imbalance for the next power storage unit. On the other hand, if variable n is equal to or greater than the number N of power storage units (YES in step S27), the determination of imbalance has been completed for all power storage units, and the process proceeds to step S28.

  Next, in step S28, the second preliminary determination unit 333 compares the timer value T of the timer circuit 337 with the monitoring time Tlim as in step S12 (step S28). When the timer value T is equal to or longer than the monitoring time Tlim (YES in step S28), the process is forcibly terminated without shifting to the final determination process. On the other hand, if the timer value T is less than the monitoring time Tlim (NO in step S28), the process proceeds to a final determination process.

  Next, the third preliminary determination process will be described. FIG. 7 is a flowchart illustrating an example of the third preliminary determination process. In the third preliminary determination process, first, similarly to step S21, the third preliminary determination unit 334 determines whether or not the first determination flag Flag1 is ON (step S31). If the first determination flag Flag1 is not ON (NO in step S31), the third preliminary determination process is terminated and the process proceeds to the final determination process.

  On the other hand, if the first determination flag Flag1 is ON (YES in step S31), the process proceeds to step S32. In step S32, the third preliminary determination unit 334 substitutes “1” for the variable n (step S32).

  Next, the third preliminary determination unit 334 compares the latest voltage change amount dV (n) obtained by the inclination acquisition unit 331 with a preset reference value ε (step S33). If the voltage change amount dV (n) is equal to or smaller than the reference value ε (YES in step S33), the timer value T of the timer circuit 337 at that time is detected by the third preliminary determination unit 334 as the detected elapsed time T (n). For example, stored in the RAM (step S34), and the process proceeds to step S35.

  Since the voltage change amount dV (n) gradually decreases with time, the detection elapsed time T (n) has elapsed from the stop of charging until the voltage change amount dV (n) reaches the reference value ε. Shows time.

  On the other hand, if the voltage change amount dV (n) exceeds the reference value ε (NO in step S33), the process proceeds to step S35 without executing step S34.

  In step S35, the third preliminary determination unit 334 adds “1” to the variable n (step S35). Next, the third preliminary determination unit 334 compares the variable n with the number N of power storage units (step S36).

  If variable n is less than or equal to the number N of power storage units (NO in step S36), the process proceeds to step S33 again in order to obtain the detected elapsed time T (n) for the next power storage unit. On the other hand, if the variable n exceeds the number N of power storage units (YES in step S36), the process proceeds to step S37.

  Next, in step S37, the third preliminary determination unit 334 confirms whether or not the detected elapsed time T (n) has been stored for all the power storage units (step S37). If there is a power storage unit in which the detected elapsed time T (n) is not yet stored (NO in step S37), the process returns to step S33 again to continue acquiring the detected elapsed time T (n). On the other hand, if the detected elapsed time T (n) is stored for all the power storage units (YES in step S37), the process proceeds to step S38.

  Next, in step S38, the variable n is an absolute value of T (n) -T (n + 1), i.e., adjacent power storage units, in the range of 1 to (number of power storage units N-1) by the third preliminary determination process. The difference in detection elapsed time at is compared with the third determination value γ3 (step S38). Since the detection elapsed time changes depending on the amount of electricity stored when charging is stopped, the absolute value of T (n) −T (n + 1) increases as the difference in the amount of electricity stored in each power storage unit increases.

  If the absolute value of T (n) −T (n + 1) is larger than the third determination value γ3 (YES in step S38), it is determined that an imbalance that requires correction is generated in the stored charge amount. The third determination flag Flag3 is turned on (step S39), and the process proceeds to the final determination process.

  On the other hand, if the absolute value of T (n) −T (n + 1) is equal to or smaller than the third determination value γ3 (NO in step S38), the timer of the timer circuit 337 is determined by the third preliminary determination unit 334 as in step S12. The value T is compared with the monitoring time Tlim (step S40). When the timer value T becomes equal to or longer than the monitoring time Tlim (YES in step S40), the third preliminary determination process is forcibly terminated without shifting to the final determination process. On the other hand, if the timer value T does not reach the monitoring time Tlim (NO in step S40), the process proceeds to a final determination process.

  In step S38, an example is shown in which the difference in arrival time until the voltage change amount dV / dt of each storage battery reaches the reference value ε is obtained as the arrival time difference between adjacent storage batteries. It may be the difference between the arrival time (Tmax) and the minimum arrival time (Tmin), or may be the difference between the average arrival time (Tave) and the arrival time of each power storage unit, and the difference between the maximum and minimum arrival times and the average arrival time Also good.

  Next, an example of the final determination process will be described. FIG. 8 is a flowchart illustrating an example of the final determination process. In the final determination process, first, the final determination unit 335 determines whether or not all of the first determination flag Flag1, the second determination flag Flag2, and the third determination flag Flag3 are turned on (step S51).

  If all of the first determination flag Flag1, the second determination flag Flag2, and the third determination flag Flag3 are on (YES in Step S51), it is determined that an imbalance that requires equalization has occurred between the power storage units. Then, the equalization flag Flag4 is turned on (step S52), and the process proceeds to equalization processing. On the other hand, when any one of the first determination flag Flag1, the second determination flag Flag2, and the third determination flag Flag3 is off, it is determined that there is no imbalance that requires equalization between the electric storage units. The equalization flag Flag4 is turned off (step S53), and the process proceeds to equalization processing.

  Next, an example of equalization processing will be described. FIG. 9 is a flowchart illustrating an example of equalization processing. First, the forced discharge control unit 336 determines whether or not the equalization flag Flag4 is turned on (step S61). Next, when it is determined that the equalization flag Flag4 is on (YES in step S61), the forced discharge control unit 336 turns on all the equalization discharge signals SG1, SG2,. , Q2,..., QN are turned on to start equalization processing (step S62).

  As a result, in the above-described final determination process, an imbalance that requires equalization among the power storage units occurs in all of the three different first preliminary determination processes, the second preliminary determination process, and the third preliminary determination process. Only when the equalization flag Flag4 is turned on, the equalization processing after step S62 is started, so that the certainty of the determination of imbalance is improved and the frequent occurrence of equalization processing due to erroneous determination is prevented. can do.

  While discharging by the equalization process is being performed, power cannot be supplied from the power generation device 10 to the load device 20. In addition, if the discharge due to the equalization process is frequently performed, the power storage unit is frequently discharged, leading to an increase in energy loss and deterioration due to an increase in the number of charge / discharge cycles of the power storage unit. By preventing frequent equalization processing due to the above, it is possible to reduce the possibility of such inconvenience.

  In the final determination process described above, any one of the first preliminary determination process, the second preliminary determination process, and the third preliminary determination process has an imbalance that requires equalization between the power storage units. If it is determined that, the equalization flag Flag4 may be turned on. In this case, the leakage of imbalance detection can be reduced.

  Next, after starting the equalization process, the forced discharge control unit 336 starts the inspection of the terminal voltages V1, V2,..., VN (step S63), and simultaneously starts the timer circuit 337 (step S64). . Then, the forced discharge control unit 336 substitutes “1” for the variable n and starts a voltage test from the first power storage unit (step S65), and whether or not the nth equalized discharge signal SGn is turned on. Is determined (step S66).

  If the equalization discharge signal SGn is off (NO in step S66), the process proceeds to step S69. On the other hand, if the equalization discharge signal SGn is on (YES in step S66), the forced discharge control unit 336 It is determined whether the n-th terminal voltage Vn is equal to or lower than the target voltage α2 (step S67). If the terminal voltage Vn exceeds the target voltage α2 (NO in step S67), the process proceeds to step S69. On the other hand, if the terminal voltage Vn is equal to or lower than the target voltage α2 (YES in step S67), the forced discharge control unit 336 is performed. Turns off the equalization discharge signal SGn (turns off the transistor Qn) to finish discharging the power storage unit Bn, and stores the power storage unit number n and the end time (step S68).

  In step S69, the forced discharge control unit 336 adds “1” to the variable n (step S69), and compares the variable n with the number N of power storage units (step S70).

  If variable n is equal to or less than the number N of power storage units (NO in step S70), the process proceeds to step S66 to check the terminal voltage of the next power storage unit. On the other hand, if variable n exceeds the number N of power storage units (YES in step S70), the process proceeds to step S71.

  Next, in step S71, as in step S12, the forced discharge control unit 336 compares the timer value T of the timer circuit 337 with the monitoring time Tlim (step S71). When the timer value T becomes equal to or longer than the monitoring time Tlim (YES in step S71), the equalization process is forcibly terminated. On the other hand, if the timer value T does not reach the monitoring time Tlim (NO in step S71), it is determined whether or not there is an equalized discharge signal that is still on, that is, whether or not there is a power storage unit that is still discharging. (Step S72).

  If there is still a discharging power storage unit (YES in step S72), the processes of steps S65 to S72 are repeated. On the other hand, if there is no discharging power storage unit (NO in step S72), the equalization process is terminated. .

  As described above, the first preliminary determination process, which is a plurality of inspection methods based on the voltage change amount dV / dt that changes according to the charged amount, not the voltage difference between the conventional power storage element and the block, by the processing of steps S1 to S53. Based on the second preliminary determination process and the third preliminary determination process, the variation in the storage amount of the power storage unit is determined. Therefore, a storage element having a small change in OCV (open voltage) with respect to the change in the storage amount (SOC) was used. Even in this case, it is possible to improve the determination accuracy of the variation in the amount of stored electricity.

  The first preliminary determination process, the second preliminary determination process, and the third preliminary determination process, that is, the voltage change immediately after stopping charging, the voltage change amount after a predetermined time, and the time until the voltage change amount of a predetermined amount are reached. Although an example of utilizing was shown, using only two arbitrary processes among the first preliminary determination process, the second preliminary determination process, and the third preliminary determination process, the power storage amount imbalance is preliminary determined in the two processes In such a case, it may be determined that an imbalance of the amount of power storage has finally occurred. Also, determination methods other than the first preliminary determination process, the second preliminary determination process, and the third preliminary determination process may be combined.

  Further, it is not always necessary to provide a plurality of preliminary determination units. For example, as the imbalance determination unit, any one of the first preliminary determination unit 332, the second preliminary determination unit 333, and the third preliminary determination unit 334 is provided, and instead of the final determination unit 335, the one preliminary determination unit The determination unit may turn on the equalization flag Flag4 instead of the first determination flag Flag1, the second determination flag Flag2, and the third determination flag Flag3.

  When a variation in the amount of stored electricity is detected, the imbalance can be reduced by the equalization process, so that it is possible to suppress the life deterioration of the power storage device 40. This facilitates extending the life of the power supply device 50.

  Note that the first determination value γ1, the second determination value γ2, and the third determination value γ3 used for the determination may be values corrected based on the storage amount (SOC) of the power storage device 40, and in particular, the power storage device 40. It is preferable that the correction is made in accordance with the amount of stored electricity (SOC) and the temperature.

  The configuration of the power supply device 50 shown in FIG. 1 is not limited to the above, and any configuration having an equivalent function may be used. For example, the control unit 330 can be realized by installing a program that realizes the various processes described above and executing the program.

  Furthermore, a mode in which the charge / discharge control circuit 340 also functions as the control unit 330 is conceivable. In this aspect, the control unit 330 is realized by installing a program for implementing various processes shown in FIGS. 5 to 9 in the microcomputer constituting the charge / discharge control circuit 340 and executing the program. be able to.

  Further, the determination of the equalization start of the power storage device is not limited to the control unit 330, but may be performed by the charge / discharge control circuit 340 or the load device 20 by obtaining power storage element information from the control unit 330. There is no problem.

  In addition, although the calculation cycle of dV / dt used for the determination of the present embodiment is 1 second, it may be an arbitrary value or may be an average value of dV / dt values at predetermined intervals.

  Furthermore, as a method for obtaining the voltage difference between the storage batteries, the difference between the adjacent storage batteries is used. However, the difference between the maximum voltage drop amount and the minimum voltage drop amount between the storage batteries may be used. It may be a difference in the voltage drop amount of the power storage unit, or may be a difference between the maximum and minimum voltage drop amounts and the average voltage drop amount.

  Moreover, in the equalization process, an example in which constant resistance discharge is performed up to the target voltage value while monitoring voltage data by resistance discharge using a fixed resistor has been shown. The equalization process may be performed, or the equalization process may be performed by charging to a predetermined voltage value.

  The embodiment of the present invention disclosed this time is illustrative and is not limited to this.

  INDUSTRIAL APPLICABILITY The power storage device imbalance determination circuit, the power supply device using the power storage device, and the imbalance determination method according to the present invention are effective for power supplies and devices having a power storage device equalization process and have industrial applicability. Is.

It is a block diagram which shows an example of the structure of the imbalance determination circuit using the imbalance determination method which concerns on one Embodiment of this invention, a power supply device provided with this imbalance determination circuit, and a power supply system. It is explanatory drawing for demonstrating the change of a terminal voltage when flowing a charging current into an electrical storage element and making a charging current zero. It is a block diagram which shows an example of a structure of the voltage detection part shown in FIG. It is a block diagram which shows another example of a structure of the voltage detection part shown in FIG. 3 is a flowchart illustrating an example of an operation including a first preliminary determination process of the power supply device illustrated in FIG. 1. It is a flowchart which shows an example of a 2nd preliminary determination process. It is a flowchart which shows an example of a 3rd preliminary | backup determination process. It is a flowchart which shows an example of a final determination process. It is a flowchart which shows an example of an equalization process. It is a graph which shows the relationship between SOC of a secondary battery, and terminal voltage.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Power supply system 10 Electric power generation apparatus 20 Load apparatus 30 Power supply control apparatus 40 Power storage apparatus 50 Power supply apparatus 310 Discharge part 320,320a Voltage detection part 321 Analog digital converter 322 Switching circuit 323 Voltage measurement part 330 Control part 331 Acquisition part 332 1st preliminary determination Unit 333 second preliminary determination unit 334 third preliminary determination unit 335 final determination unit 336 forced discharge control unit 337 timer circuit 340 charge / discharge control circuit 350 imbalance determination circuit 401 power storage element B1, B2, ..., BN power storage unit Flag1 First determination flag Flag2 Second determination flag Flag3 Third determination flag Flag4 Equalization flag Q1, Q2, ..., QN Transistors R1, R2, ..., RN resistors SG1, SG2, ..., SGN Equalization discharge Signal T Timer value V1, V2,.・ VN terminal voltage dV (1), dV (2), ..., dV (N) Voltage change amount α1 Reference voltage α2 Target voltage β Setting time γ1 First judgment value γ2 Second judgment value γ3 Third judgment value ε reference value

Claims (15)

A voltage detection unit for detecting a terminal voltage in each of the plurality of power storage units;
Voltage gradient information indicating a change amount of each terminal voltage per predetermined time from each terminal voltage detected by the voltage detection unit while stopping the charging while charging the plurality of power storage units. An inclination acquisition unit that performs an inclination information acquisition process to be acquired;
An imbalance determining unit that determines whether or not an imbalance in the amount of electricity stored in the plurality of power storage units has occurred using a plurality of pieces of voltage gradient information corresponding to the terminal voltages acquired by the gradient acquiring unit; An imbalance determination circuit comprising: The imbalance determination unit
A plurality of preliminary determinations that preliminarily determine whether or not there is an imbalance in the amount of power storage in the plurality of power storage units, using a plurality of voltage gradient information acquired by the gradient acquisition unit by different determination processes And
2. A final determination unit that finally determines whether or not an imbalance of the amount of electricity stored in the plurality of power storage units has occurred based on determination results by the plurality of determination processing units. The imbalance determination circuit described. One of the plurality of preliminary determination units is:
Immediately after the charging is stopped, when the difference between the pieces of voltage gradient information acquired by the gradient acquisition unit exceeds a preset first determination value, it is preliminarily determined that the imbalance has occurred. The imbalance determination circuit according to claim 2, wherein: One of the plurality of preliminary determination units is:
When a preset set time has elapsed since the stop of charging, when the difference between the respective voltage slope information acquired by the slope acquisition unit exceeds a preset second determination value, the imbalance The imbalance determination circuit according to claim 2, wherein the determination is made in advance as follows. One of the plurality of preliminary determination units is:
When each voltage gradient information acquired by the gradient acquisition unit becomes equal to a preset reference value, a difference between elapsed times from the stop of charging is set to a preset third determination value. 5. The imbalance determination circuit according to claim 2, wherein when it exceeds, it is preliminarily determined that the imbalance occurs. The final determination unit
When all of the plurality of preliminary determination units determine that the imbalance has occurred, the preliminary determination unit finally determines that the imbalance has occurred. The imbalance determination circuit described in 1. The final determination unit
When at least one of the plurality of preliminary determination units determines that the imbalance has occurred, it finally determines that the imbalance has occurred. 2. The imbalance determination circuit according to item 1. The power storage unit is
The imbalance determination circuit according to any one of claims 1 to 7, wherein the amount of decrease in the terminal voltage per predetermined time after the charging is stopped increases as the amount of stored electricity increases. . The power storage unit is
The imbalance determination circuit according to claim 8, which is a lithium ion secondary battery using olivine-based lithium composite phosphate as the positive electrode active material. The positive electrode active material is
Li _X A _Y B _Z PO ₄
(A is at least one of Me, Fe, Mn, Co, Ni, Cu,
B is at least one of Mg, Ca, Sr, Sc, Y, Ti, Zr, V, Nb, Cr, Mo, W, Ag, Zn, In, Sn, and Sb, 0 <X ≦ 1, 0.9 <= Y <= 1, 0 <= Z <= 0.1) The imbalance determination circuit of Claim 9 characterized by the above-mentioned. The inclination acquisition unit
The slope information acquisition process is performed when each terminal voltage detected by the voltage detection unit exceeds a preset reference voltage. Equilibrium judgment circuit. The voltage detector is
The imbalance determination circuit according to claim 1, further comprising: a plurality of voltage measurement units that detect terminal voltages of the power storage units. The voltage detector is
One voltage measuring unit for detecting a terminal voltage of each power storage unit;
12. A switching unit that switches a connection relationship between the voltage measuring unit and each power storage unit and causes the voltage measuring unit to detect a terminal voltage of each power storage unit. 12. The imbalance determination circuit according to claim 1. An imbalance determination circuit according to any one of claims 1 to 13,
The plurality of power storage units;
A discharge part for discharging each of the plurality of power storage units;
When it is determined by the imbalance determining unit that the imbalance has occurred, each of the discharge voltages by the discharging unit until each terminal voltage detected by the voltage detecting unit is equal to or lower than a preset target voltage. A power supply apparatus comprising: a forced discharge control unit that discharges the power storage unit. A step of detecting a terminal voltage in each of the plurality of power storage units by the voltage detection unit;
The inclination acquisition unit stops the charging during charging of the plurality of power storage units, and calculates a change amount per predetermined time of each terminal voltage from each terminal voltage detected by the voltage detection unit while the charging is stopped. Performing a slope information acquisition process for acquiring each of the voltage slope information shown;
The imbalance determination unit determines whether or not an imbalance of the storage amount of the plurality of power storage units has occurred using a plurality of voltage gradient information corresponding to each terminal voltage acquired by the gradient acquisition unit. A method for determining imbalance, comprising the steps of:

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